Safety lathe dog



J. D'. KARLE f SAFETYALATHE Dos Filed July 1924 June 8 19,26.

wvl-:mon Jbn Kade. M

" Arronnnv Patented .lune 8,

UNITED- sTATii-is ypii-T13.;NTY0111.-;|.;

' .ronn'nxAnnm'on RosELLErARK, New '.iERsmr.

SAFETY L-A'rnn nos.V`

i I 'Application f lediJuly 3,

Y insertion and removal 'ot `a Afairrangev or sizes of work wit'hifgreaterfacility' and rapidity than was heretofore possible.

'A further aim of this invention is to provide a safety-dog capable of securely gripping circular as Well as slab-sided work1 wherein the `work-gripping' action is augmented in use by the machine-operation upon the work regardless of tl'ie'direction of'rota tionther'eof. f n* Other objects lofthe invention will be apparent from the followingadescriptin and c alms'. n f f In its preferred embodiment they present improved lathe-'dog comprises a vbodyv from which proj-ects'- the usual driving-tail and which body .is-provided with a work-receiving aperture defined by convergingV sidewalls. Positioned upon the` lathe-dog body tof projectv within the work-'receiving aperture is fa circulary friction-Cami which; is journaled'forrotation upon an axis disposed" eccentric to the peripheralsurface of the' friction-cam. 'This friction-cam' yis journaled upon aV slide-block adj'ustably-s'ecured uponvv the lathe-dog bOd-yfto permit of ready manual manipulationto alter v.the gripping' position-fof thecam for -various sizes of work. Thec'onverging sidewalls of the` work-receiving aperture', together' with Vthe ,friction-cam peripheral surface, afford in eEect 'a three-point' engagement with the work, relative rotation in either direction of the workfand the gripping surfaces eect-ing a secure gripping of the work. This construction not only greatly facilitates insertion and removal of the work and thereby,V

speeds production, but also conforms strict` ly to the modern requirements in eliminating dangerous work-securing projections such as set-screws and the like. 'v

In the accompanying drawings,-F ig. 1 is a perspective view of one form of the present improved lathe-dog, with the parts shown in detached relationship. Flg. 2 `1s a longitu- 1924. Serial .No. y77235983. J

dinal sectional view of the lathe-dog illus- A' trating-its work-gripping action, yand Fig. 3

is a side elevation of the improved lathe-dog.

Referringto tlierdrawings, the present construction comprises the stock 0r body 1 from vv'which .projects `a common form of driving-tail "2, although Vother forms of driving-tails may obviously be employed. The body 1 isprovided with a `work-receiving aperture having converging side-walls t comprising work-gripping'surfaces against which lthe-work 5l is forced by a rotaryl circular frictincam 6 'disposed'opposite to the apex 't' ofthe aperture. The friction-'cam 6 is so disposed upon thej aw that 'in its operative position-its knurled peripheral-'surface 8 projects within-the aperture 3, said peripheral-surface Bbeing eccentric to the axis` of rotation of thefriction-cam. l l' The friction-cani 61 is' Vvsho-wn alsjournaled upon apin 9 disposed'lupona slide-block 10 to intersect a cam-receiving slot 11 provided in said slide-block.` Y Thel slide-block 10 is slidinglyffitted within afrectangular guide-y wayf provided inf the-body" land isi confined to`4 oppositely directed 'movementsfther'e Y .in by a cover-plate `131 secured upon the body 1 screws,"as 141` The'slide-block 10 is provided' withy a ythreaded 4aperture' 15 en-k tered byanadjustingscrewf 16, thefknurled head1? f of whiclris provided with a'plurality' of peripheral `apertures y18 and pro# jects through 'aftra-nsverse slot 19 provided inthe body 1, thereby holding thescrew 16 against endwise movement when. rotated'v and consequentlyeifectingfadjustment of the slideblock.. To providet for vmoreyready accessto the screw-head 17 without unduly f enlarging the same, the body'l adjacent the head. 17 maybe beveled as at 2O',` this construction-keeping thescrew-head 17 from projecting anyv appreciableextent beyond the outer limitsof the jmaineplortion ofthe body 1. In order to klimit the advancing movementjof the slide-block 10 to prevent accidental detachment ofthe screw 16 ftherefrom," saidslide-block is provided with a stop-pin 21 disposed in a slot 22A formed in the cover-plate 13, the limit of'advancing movement,` being evidently determined by the inner end of the slot. f

It will be apparent that when the slide-v relative rotary movement between the work and the lathe-dog will cause rotation of `the friction-cam. This rotation of the cam will obviously effect a secure gripping of the work at three points, one of which lies in the periphery of the cam and one in each ofthe converging surfaces 4. Should no-w a machining operation be attempted upon the work in a manner such that the operating tool has va tendency to rotatet-heV work in the same direction as that in which it was turned to grip it in the dog, the tool-action will lmerely augment the gripping action of the friction-cam upon the work, whereby the Work is firmly held against slippage. Nevertheless, after the machining operation is completed, a slight turning of the work in the opposite direction will immediately i release it from the friction-cam.

Any given adjusted position of the friction-cam will evidently accommodate a moderate degree of variation in sizes of the work without further adjustment. The adaptability of the .present improved lathe-dog to different sizes of work is particularly ad- J vantageous owing tothe saving of time obtained, all that is necessary being the insertion lof the Work within the. dog and the action of the machine-tool will itself cause the work to be instantly and securely gripped regardless of theA direction of rotation of the work., Y

When the rangevin work-sizes is greater ythan canbe accommodatedby the eccentricif` ty ofthe friction-cam in a given adjustedr position, it is onlyV necessary to reposition the same by manipulating the head 17 o-f the screw 16. For certain classes of work, such as cutting screw-threads, the tool action upon the work is successively in reverse directions and the reversal of the direction of action of the tool would tend to release the work from the dog and then immediately cause aV regripping thereof. This slight period of nonerot-ation of the work may be undesirable for certain operations and when workof this character is positioned in the aperture 3, a suitable tool may be inserted in any one of the eripheral apertures 18 in the screw-head l and the screw vfurtherl rotated whereby the work is so firmly gripped by the consequent jamming action that loosening of the work underthe reverse l. A safety lathe-dog including a body.A

having awork-receiving aperture, an. eccentrically-journaled peripherally-circular frict1on-cam dlsposed upon said body for complete rotation inopposite directions and 'projecting within said aperture to grip work by relative rotationv between the work and lathe-dog in. either of two opposite directions, and manually adjustable means for shifting the axis of rotation of said cam tol predetermine its degree of projection within said aperture.

2. A safety lathe-dog including a body having aworlr-receiving aperture, a rotary friction-cam disposed upon said body for complete rotation in opposite directions pro-` jecting 4within said aperture, and manually adjustable means for determining the degree of projection within said aperture of the friction-cam to accommodate different sizes of work.

3. A. safety having a work-receiving aperture, a rotary friction-cam disposed vupon said body to project within said aperture, an adjusting screw held against endwise movement on said body for determining the degree of projection within. said aperture of thel friction-cam, and a stop for limiting the degree ofY adjustment effected by manipulation of said screw. 4. A safety lathe-dog comprising a body free of projecting set-screws having a work-- receiving VAaperture defined by convergent work-engaging surfaces, a friction-cam opposedto said surfaces, a slide-block rotative.

ly sustaining Vsaid friction-cam, a guid'eway f in said body for the slide-block, and an adiv justing-screw threaded into saidv slide-block for determining the position ofthe frictioncam with respect to said surfaces, said adlathe-dog including aibody Y justing screw having vits manipulating head disposed within a transverse slot provided inthe lathe-dog body'whereby the screw is vheld against endwise movement.

In testimony whereof I affix my signature.

JOHN D. KARLE. 

